We must fight because there is no way they can enforce it without creating a registration which is already illegal.
Also, here's how a "universal background check" would play out in America:
All sales through gunshops.
Gunshop: "Wow we're overwhelmed, transfer fees are now $100" (on my $25 shotgun)
Gubmint: "Whoa, let's cap the transfer fees at $25 so people aren't in an uproar."
Gunshop: "I can't tie up all my time and employees in this for $25, we're no longer offering transfer services."
Private sales are now illegal.
Yes there will be some that continue to do it, but the lines will be out the doors and it will takes days just to do a transfer that right now requires 5 minutes of your time at no cost. People won't stand for it.
Anyways, didn't mean to get too far off topic.
P.S. Listen to Warp, giving ground never permanently appeases the gun control folks. We tried that during the past main gun control acts, (NFA, etc.)